91 lines
5.4 KiB
Markdown
91 lines
5.4 KiB
Markdown
---
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id: 5a24c314108439a4d4036154
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title: Combine Multiple Reducers
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challengeType: 6
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isRequired: false
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videoUrl: ''
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localeTitle: 结合多个减速器
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---
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## Description
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<section id="description">当您的应用程序的状态开始变得更加复杂时，可能很容易将状态分成多个部分。相反，请记住Redux的第一个原则：所有应用程序状态都保存在商店中的单个状态对象中。因此，Redux提供减速器组合作为复杂状态模型的解决方案。您可以定义多个reducers来处理应用程序状态的不同部分，然后将这些reducer组合成一个根reducer。然后将根reducer传递给Redux <code>createStore()</code>方法。为了让我们将多个reducer组合在一起，Redux提供了<code>combineReducers()</code>方法。此方法接受一个对象作为参数，您可以在其中定义将键与特定reducer函数关联的属性。 Redux将使用您为密钥指定的名称作为相关状态的名称。通常，当每个应用程序状态以某种方式不同或唯一时，为每个应用程序状态创建一个减速器是一个好习惯。例如，在具有用户身份验证的笔记记录应用程序中，一个reducer可以处理身份验证，而另一个reducer处理用户正在提交的文本和备注。对于这样的应用程序，我们可能会像这样编写<code>combineReducers()</code>方法： <blockquote> const rootReducer = Redux.combineReducers（{ <br> auth：authenticationReducer， <br>笔记：notesReducer <br> }）; </blockquote>现在，关键<code>notes</code>将包含与我们的注释相关联的所有状态，并由<code>notesReducer</code>处理。这就是如何组合多个reducers来管理更复杂的应用程序状态。在此示例中，Redux存储中保存的状态将是包含<code>auth</code>和<code>notes</code>属性的单个对象。 </section>
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## Instructions
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<section id="instructions">代码编辑器中提供了<code>authReducer()</code> <code>counterReducer()</code>和<code>authReducer()</code>函数以及Redux存储。使用<code>Redux.combineReducers()</code>方法完成<code>rootReducer()</code>函数的<code>Redux.combineReducers()</code> 。指定<code>counterReducer</code>一键叫<code>count</code>和<code>authReducer</code>一个叫关键<code>auth</code> 。 </section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: <code>counterReducer</code>应该递增和递减<code>state</code> 。
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testString: 'assert((function() { const initalState = store.getState().count; store.dispatch({type: INCREMENT}); store.dispatch({type: INCREMENT}); const firstState = store.getState().count; store.dispatch({type: DECREMENT}); const secondState = store.getState().count; return firstState === initalState + 2 && secondState === firstState - 1 })(), "The <code>counterReducer</code> should increment and decrement the <code>state</code>.");'
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- text: <code>authReducer</code>应切换在<code>true</code>和<code>false</code>之间进行<code>authenticated</code>的<code>state</code> 。
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testString: 'assert((function() { store.dispatch({type: LOGIN}); const loggedIn = store.getState().auth.authenticated; store.dispatch({type: LOGOUT}); const loggedOut = store.getState().auth.authenticated; return loggedIn === true && loggedOut === false })(), "The <code>authReducer</code> should toggle the <code>state</code> of <code>authenticated</code> between <code>true</code> and <code>false</code>.");'
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- text: 存储<code>state</code>应该有两个键： <code>count</code> ，它包含一个数字， <code>auth</code> ，它包含一个对象。 <code>auth</code>对象应具有<code>authenticated</code>属性，该属性包含布尔值。
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testString: 'assert((function() { const state = store.getState(); return typeof state.auth === "object" && typeof state.auth.authenticated === "boolean" && typeof state.count === "number" })(), "The store <code>state</code> should have two keys: <code>count</code>, which holds a number, and <code>auth</code>, which holds an object. The <code>auth</code> object should have a property of <code>authenticated</code>, which holds a boolean.");'
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- text: 该<code>rootReducer</code>应该是结合了功能<code>counterReducer</code>和<code>authReducer</code> 。
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testString: 'getUserInput => assert((function() { const noWhiteSpace = getUserInput("index").replace(/\s/g,""); return typeof rootReducer === "function" && noWhiteSpace.includes("Redux.combineReducers") })(), "The <code>rootReducer</code> should be a function that combines the <code>counterReducer</code> and the <code>authReducer</code>.");'
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='jsx-seed'>
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```jsx
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const INCREMENT = 'INCREMENT';
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const DECREMENT = 'DECREMENT';
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const counterReducer = (state = 0, action) => {
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switch(action.type) {
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case INCREMENT:
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return state + 1;
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case DECREMENT:
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return state - 1;
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default:
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return state;
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}
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};
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const LOGIN = 'LOGIN';
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const LOGOUT = 'LOGOUT';
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const authReducer = (state = {authenticated: false}, action) => {
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switch(action.type) {
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case LOGIN:
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return {
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authenticated: true
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}
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case LOGOUT:
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return {
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authenticated: false
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}
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default:
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return state;
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}
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};
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const rootReducer = // define the root reducer here
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const store = Redux.createStore(rootReducer);
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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// solution required
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```
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</section>
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